Power supply device for out putting stable programmable power supply

Abstract

The present invention discloses a power supply device for outputting a stable programmable power supply, which comprises a transformer disposed at a DC output end of the power supply device, and a clamp circuit connected to a secondary current of the transformer. Since the clamp circuit is disposed on the secondary current of the transformer, therefore it does not require a high DC voltage to drive the clamp circuit. The clamp circuit can release the high voltage produced when the metal oxide semiconductor field effect transistor (MOSFET) is off, and thus reducing the high voltage borne by the MOSFET to enhance the reliability of the MOSFET. Additionally, the present invention can prevent the transformer from being saturated due to magnetic leakage, inductance, and stored energies released or eliminated from the transformer.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a power supply device for outputting a stable programmable power supply, more particularly to a power supply device using a clamp circuit connected to the secondary current of a transformer, such that when the metal oxide semiconductor field effect transistor (MOSFET) is off, a high voltage can be released through the clamp circuit, and thus lowering the high voltage borne by the MOSFET and enhancing the reliability of the MOSFET. BACKGROUND OF THE INVENTION [0002] In general, a switching power supply is extensively used for providing power supply. Most of the traditional power supply devices are linear power supply devices, which are usually used for an instrument providing a constant voltage and a constant current, which has a low ripple noise, a low EMI, a good modulation, and an easy-to-control features. Although the linear power supply device is popular, yet it still has certain shortcomings including a large power ...

AI Technical Summary

Benefits of technology

[0010] The primary objective of the present invention is to provide a power supply device for outputting a stable power supply, which comprises a clamp circuit connected to the Another Aspect Circuit of the transformer of the power supply device for releasing a high voltage produced when the MOSFET is off and the energy produced by the magnetic leakage and the inductance and then stored in the transformer in order to lower the high voltage borne by the MOSFET and enhance the reliability of the MOSFET.

[0012] A further objective of the present invention is to provide a power supply device for outputting a stable power supply, which comprises a voltage divider circuit connected to a DC power supply of a rectify / filter circuit disposed at the input terminal of the power supply device, and the voltage divider circuit is also connected to an input terminal of an IC of the pulse width modulator, so that if a voltage OVRV exceeds a predetermined value due to an excessively high AC power supply, the OVRV will turn off the MOSFET to protect the power supply device and avoid damages caused by the high voltage. In the same time, the present invention will also provide a bias voltage circuit for the primary driver circuit of the transformer.

[0013] Another objective of the present invention is to provide a power supply device for outputting a stable power supply, which comprises a buffer circuit connected to the MOSFET, and the buffer circuit can prevent the high voltage of a pulse caused by the reverse direction of the primary voltage of the transformer when the transformer turns off the MOSFET to pierce through or damage the MOSFET. Therefore, the charging by a capacitor can slow down the instant change of voltage. If the MOSFET is turned ON, then the diode is substantially in a forward bias voltage, and the capacitor is discharged to consume the power of the pulse current to protect the MOSFET and reduce the generation of electromagnetic interference signals.

Problems solved by technology

Although the linear power supply device is popular, yet it still has certain shortcomings including a large power loss and a low power efficiency.

Further, since the volume of the power supply device used for the instrument is large and inefficient, therefore it is a trend of using a switching-mode technique for the manufacture of the power supply device for instruments, and such technology is used to provide a power density and a power efficiency.

However, the traditional linear power supply device generally uses a transistor working in a linear area and using it as a rheostat to modulate unstable input voltages.

Therefore, the total system power loss will be increased, and the efficiency will drop.

However, the switching power supply does not work completely in the linear area.

Since the current is stored in the transformer T1, the transformer T1 will be worn out tremendously.

In addition, although the primary terminal of the transformer is connected to a clamp circuit (comprised of D2 and D3) for clamping the voltage of the passing current, it still results in a lower efficiency than the original efficiency since the voltage of the primary current is higher.

Furthermore, D2 and D3 must be a high voltage resisting diode, and its cost is higher than that of the general diodes.

Although the forward circuit can reduce the primary and secondary current passing through the transformer which can reduce the copper loss of the transformer, the transformer adds a third coil and thus increases the cost.

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